The following patch fixes https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115013
Successfully tested and bootstrapped on x86-64.
commit 44430ef3d8ba75692efff5f6969d5610134566d3 Author: Vladimir N. Makarov <vmaka...@redhat.com> Date: Mon May 13 10:12:11 2024 -0400 [PR115013][LRA]: Modify register starvation recognition My recent patch to recognize reg starvation resulted in few GCC test failures. The following patch fixes this by using more accurate starvation calculation and ignoring small reg classes. gcc/ChangeLog: PR rtl-optimization/115013 * lra-constraints.cc (process_alt_operands): Update all_used_nregs only for winreg. Ignore reg starvation for small reg classes. diff --git a/gcc/lra-constraints.cc b/gcc/lra-constraints.cc index e945a4da451..92b343fa99a 100644 --- a/gcc/lra-constraints.cc +++ b/gcc/lra-constraints.cc @@ -2674,8 +2674,9 @@ process_alt_operands (int only_alternative) if (early_clobber_p || curr_static_id->operand[nop].type != OP_OUT) { - all_used_nregs - += ira_reg_class_min_nregs[this_alternative][mode]; + if (winreg) + all_used_nregs + += ira_reg_class_min_nregs[this_alternative][mode]; all_this_alternative = (reg_class_subunion [all_this_alternative][this_alternative]); @@ -3250,6 +3251,7 @@ process_alt_operands (int only_alternative) overall += LRA_MAX_REJECT; } if (all_this_alternative != NO_REGS + && !SMALL_REGISTER_CLASS_P (all_this_alternative) && all_used_nregs != 0 && all_reload_nregs != 0 && (all_used_nregs + all_reload_nregs + 1 >= ira_class_hard_regs_num[all_this_alternative]))